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QUIZ, PUZZLES & TRICKS
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TWO ' ROPE AND RING' TEASERS

Here is the first one of those teasers and  this is the second one.

Can you explain simply (make it simple but not simpler than necessary as Einstein said) :

- the reason why for the first it is intuitively evident that you can get the ring off the turk's head

and

- why  is it impossible to get it off in the second ?

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PLAYING WITH THE PERKO PAIR (no not the fille au pair !)

A small topology desensitization game.

Make one of these two knots (yes you will have to 'close' the knot to be at ease).

Only using smooth continuous changes , Reidemeister's moves, ( one - two - three) with no rethreading, no cutting, no gluing, give it the appearance of the other.
By doing that you will show that they are "equivalent".

You can try to use this more recent aspect of the Perko pair instead of the first given one.

They are said "the PERKO pair" after the name of the astute person who shown that they were *not* two distinct knots ; just a someone seen in full face and the same someone seen in profile are not distinct individuals.
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A FIXED LOOP IS EQUIVALENT TO A SLIPPING LOOP
or
BOWLINE (considered to be a fixed loop) TRANSMOGRIFIED INTO A NOOSE

Do not open this link at the moment  but  'rope in hands' try to find how you would proceed to get  a noose / sliding loop with a bowline.

I very much doubt that a loaded bowline could have this behaviour, it still remain that it is easy to do it with a bowline in a *very relaxed* 'setting'.

Using 'le noeud de chaise préparé' / the prepared bowline (#1788), 
some of the time you may get this result without even trying!
So please, just as while scuba diving one must always verify that one's action has the
intended result with the environment as reference, when making a bowline 'prepared"
carefully verify the resulting knot before putting it into use.

Conclusion :
BEWARE of  "written in stone" classification and of the "admitted idea that every one know":
a fixed loop is sometime (equivalent to) a slipping loop or noose and that without
any  rethreading of the knot ! just a question of "arranging, dressing it'.

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JUST BY SUBTLY MODIFYING ( wantonly or inadvertently) # 1788 GET A
LAP/LAPP BOWLINE OR AN OUTSIDE TAIL Bwl INSTEAD OF THE USUAL INSIDE TAIL ONE.


Look at ABoK #1788, this is what is named here in France "le noeud de chaise préparé" in other words  'the prepared Bwl'

Subtly change either crossing(s)  and/or the way the WEnd ( Working End)  is thread in so as to get the 2 other types

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QUIZ :  BOWLINE ON A RING

Knots at the end of blue rope cannot pass through the ring.

Will you be able to hitch a bowline on the ring and end with that ?
Full solution can be found here.
 

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Copyright 2005 Sept - Charles Hamel / Nautile -
Overall rewriting in August 2006 . Copyright renewed. 2007-2014 -(each year of existence)

Url : http://charles.hamel.free.fr/knots-and-cordages/